server{
    listen 80;
    location / {
        proxy_pass http://localhost:2000;
    }
}

ll /etc/nginx/sites-enabled/bbs
/etc/nginx/sites-enabled/bbs -> /var/www/bbs/bbs.nginx

server nginx restart

gunicorn wsgi --bind 0.0.0.0:2000 --pid /tmp/bbs.pid

[2018-05-20 01:12:31 +0800] [1311] [INFO] Starting gunicorn 19.8.1
[2018-05-20 01:12:31 +0800] [1311] [INFO] Listening at: http://0.0.0.0:2000 (1311)
[2018-05-20 01:12:31 +0800] [1311] [INFO] Using worker: sync
[2018-05-20 01:12:31 +0800] [1314] [INFO] Booting worker with pid: 1314

[1]  + 1311 suspended  gunicorn wsgi --bind 0.0.0.0:2000 --pid /tmp/bbs.pid

---

run commands in the background without affecting terminal input. You can use the & symbol at the end. For example,

gunicorn wsgi --bind 0.0.0.0:2000 --pid /tmp/bbs.pid &

service, for restarting the service is not server!

service nginx restart

use the following instruction to check that the configuration file is correct before restarting:

service nginx configtest

After

starts, check / var/log/nginx/error.log to see if there is any error message.

---

< H2 > first of all, your deployment ideas are not clear. < / H2 >

next, try to illustrate it with the simplest example.

< H2 > scene settings: < / H2 >

operating system: ubuntu 18.04 LTS
ignore the firewall and
AppArmor
python the environment is managed using pythonenv , the path is / home/username/.virtualenvs/hello
assume that my Flask application is as follows / home/username/project/hello.py (excerpted from Flask official documentation):

-sharp hello.py
from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

< H2 > question: how do I make gunicorn run (daemonize) in the background? < / H2 >

running gunicorn, directly on the command line is only suitable for development or debug scenarios, and the production environment requires gunicorn to run (daemonize) in the background.
of course, you can run the following command directly under terminal to force gunicorn to run in background mode (&).

gunicorn --bind /run/gunicorn/socket --pid /run/gunicorn/pid hello:app &

however, this mode has inherent defects, such as making gunicorn dependent on the terminal, that runs it from the point of view of reliability (for example, when the terminal process running it dies, gunicorn also dies) and availability (for example, gunicorn cannot run automatically after a system restart), make this method unsuitable for use in a production environment.
remarks : -- bind parameter value of gunicorn is set to / run/gunicorn/socket instead of 0.0.0.0 code 2000, because the performance of unix socket is higher than tcp port . When nginx and gunicorn are not on the same host, you can only use tcp port .

< H2 > one of the solutions systemd < / H2 >

create the following file / etc/systemd/system/gunicorn.service , with the following contents:

[Unit]
Description=gunicorn daemon
After=network.target

[Service]
PIDFile=/run/gunicorn/pid -sharp PID
User=www-data -sharp 
Group=www-data -sharp 
RuntimeDirectory=gunicorn -sharp /run
WorkingDirectory=/home/username/project -sharp 
ExecStart=/home/username/.virtualenvs/hello/bin/gunicorn --pid /run/gunicorn/pid \
          --bind unix:/run/gunicorn/socket hello:app -sharp gunicorn
ExecReload=/bin/kill -s HUP $MAINPID
ExecStop=/bin/kill -s TERM $MAINPID
PrivateTmp=true

[Install]
WantedBy=multi-user.target

run the following command to start the gunicorn service and make it boot automatically.

sudo systemctl enable --now gunicorn.service

run the following command to view the status of the gunicorn service.

sudo systemctl status gunicorn.service

remarks : in addition to systemd , you can also use supervisor to manage gunicorn (self Google ).

< H2 > nginx Settings < / H2 >

server {
    listen 80;
    server_name www.yourhostname.com;
    location / {
        proxy_pass http://unix:/run/gunicorn/socket;
    }
}